Tunable magnetron



Jan, 11, 1949. H. c. JONAS ETAL TUNABLE MAGNETRON' 3 Sheets-Sheet 1 Filed March 7, 1945 y ac Jon/As /NvE/vrons ALA/co Y n d -"""P1x|-h lll. l 'Il l ...2. u K 4 .f Y 4 Y s ...v ...v f, Mv.. .N ,y 1. .Y A. l c.. s l ...i

ATTORNEY Jan@ 11, 1949.

H. c. JONAS ET A1.

TUNABLE MAGNETRON 5 Sheets-Sheet 5 Filed March 7, 1945 Avv j .JON /Nl/EN7ORS LA/CAOS x 1.. Ro/vc/ ma@ 5.7M

ATTORNEY Patented Jan. 11,1949 :ffl-qa ,UNITED STAT TUNABILE MAGNETRON Herbert C. Jonas, Great Neck, N. Y., Joseph P. Laico, Springfield, N. J., and Victor L. Ronci, New York, N. Y.,lassignors to Bell Telephone` Laboratories, Incorporated, New York, N. Y., acorporation of NewYork Application March 7, 1945, Serial No. 581,410

' v5 claims. (o1. 315-39)` This invention relates to tunable magnetrons 4 u and more particularly to magnetrons of the multicavity type.

Objects of this invention are toimprove th construction of multicavity magnetrons, to increase the efficiency of the magnetic system of such devices and to enable accurate tuning o f the several cavity resonators thereof.

In one illustrative embodiment of this invention, a magnetron comprises a body assembly including an annular anode having a plurality of parallel, resonant cavity dening bores therein, a cathode in cooperative relation with the anode, a magnetic system for producing a magnetic field parallel to the cathode and in the anode-cathode region, and means for altering the' effective volume of the bores thereby to tune the cavity resonators defined thereby. i

In accordance with one feature of this invention, the magnetic system comprises a pair of vmagnetic pole-pieces sealed'to the body assembly and defining portions of an enclosing vessel therewith, one of the pole-pieces mounting the cathode and the other pole-piece mounting the The invention and the above-noted and other features thereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawing in which: y

Fig. 1 is a perspective view of a magnetron illustrative of one embodiment of this invention; Fig. 2 is a plan view, mainly in section, of the magnetron illustrated in Fig. 1;

Fig. 3 is an end view of the magnetron, portions of the output line and wave guide `being broken away; and

Fig. 4 is an enlarged perspective view mainly in section showing details of the anode and portions of the resonator tuner associated therewith. Referring now to the drawing, the magnetron therein illustrated comprises basically four cooperatively associated assemblies, specifically body and anode, input, output and tuner assemblies. The body and anode structure comprises a rectangular metallic block Ill,4 for. exampleoi 2 copper, having a central cylindrical bore Il therethrough and having also a plurality of integral heat radiating ns I2, and a cylindrical anode I3, for example also of copper, tted coaxially within the boreand brazed thereto, Ad- -vantageously the wall portion of the bore engaged by the anode is knurled to provide a tight push fit of the anode therewith, whereby the anode may be positioned accurately and rmly within the body prior to the brazing of the anode to the body.

`The anode I3 is provided with anaxial cylindrical aperture I4 and also with a plurality of identical, equally spaced bores I5 dening a group of cavity resonators arranged symmetrically about the axial aperture I4. A vplurality of arcuate, metallic coupling straps I6 are secured to the ends of the anode I'3 and serve to X the mode of excitation of the several cavity resonators as described in Patent 2,447,537, issued August 24, 1948, to Victor L, Ronci, and application Serial No. 529,619, filed April 5, 1944, of J. B. Fisk.

The input assembly comprises a pole-piece Il, for example of steel, having a cylindrical head portion I8 fitted Within the bore II, an annular seat I9 aiiixed, as by brazing, to one end `of the body I0 and a central aperture 20 coaxial with the-"head I8 and, thus, with thel aperture I4. Sealedin a recess in the outer end of the pole# piece I1" is a cup-shaped metallic member 2l to which a vitreous stem 22 is sealed, the stem having sealed `thereto an elongated metallic tube 23 to the inner end of which a tubular member 2d is joined. The member 24 is positioned coaxially with respect to the cylindrical head I8 and, thus, is coaxial with the aperture I4, into which it extends. Fitted upon the member 24 and affixed thereto is a cathode member having a cylindrical sleeve portion 25 coated on its outer surface with electron emissive material, and having also a pair of integral discs 26. Within the cathode member is a'helical heater filament 2l one end of which is connected to the tubular member 24 and theother end of which is connected to a leading-in conductor28 positioned within the tube 23 and tubular member 24 by an insulating sleeve 29. The conductor 28 and tube 23 are connected to terminal jacks 3l] by wires 3l, the jacks' 30 4being carried by an insulating shell 32 mounted upon a plate 33 afxed to the pole-piece I'l, as'by brazing.

The output assembly comprises a -metallic coupler 83 having a seating surface 34 ailixed, aS'by brazinato one side of the body lo and having also a cylindrical plug portion 35 secured in an aperture in the body I0. Advantageously, a part of the outer surface of the plug portion 35 is knurled to provide a tight fit between this portion and the aperture wall. The coupler 83 has sealed thereto a vitreous stem 31 having a transverse rectangular bead 38 sealed therein, into which a linear output conductor 39, accurately coaxial with the plug portion 35, is sealed. The inner end of the conductor 39 is bent to form a loop 4I which is opposite and parallel to one end of the anode I3 and aligned with one of the cavity resonator defining bores I5.:

The coupler mounts a cylindrical 4conductorf, which is coaxial with the conductor 39 rand deiines therewith and the coupler a coaxial output line. This line is coupled to a wave guide ele ment 44 of rectangular cross-section, the axis of 81 secured to the 4plate by screws 68, only two of which are shown. Thus, it will be seen that the bearing ring 65 is floatingly mounted whereby automatic self-centering thereof is realized.

The head 60 has secured thereto, as by screws 69, ahelicalgear which is-cooperatively associated with aworm :gear 1I supported from a pair of arms or brackets 12 extending from the mounting plate 6I. The worm gear 1I when rotated drives the helical gear 10 to effect rotation of the screw 59 and, hence, axial motion of the driving member 51 and tuning pins 52,

i whereby the resonant frequency of the cavity resonators defined by the bores I5 is adjusted this element being at right angles to the axis of the coaxial line and passing through the center of the bead 38. One end of the Aguide element 44 is closed by a tuning plug 45 aiiixed to the Vguide element, as by soldering, and which, during the fabrication of the ydevice and prior to being fixed in place, is positioned to fix the electrical length oi the guide element at a prescribed value. The guide element 'is provided with a iiange 46 for vcoupling to a suitable wave guide. 1

The tuner assembly comprises a pole-piece, for example of steel, having a rectangular body portion 41 seated upon one `end of the Vbody IB and a cylindrical portion 48 iitted to an adapter ring Sgthe ring 49 iitting within the aperture II `in the body it to locate the `cylindrical portion 48 in accurate coaxial alignment with the Vanode I3. The pole-piece, adapter ring and body are secured to one another as by a gasket Vof solder indicated at 5t).k The cylindrical portion 48 is provided with a plurality of aperturesV 5I, one for each of the bores I5 and axially aligned't'herewith. Extending through each aperture 5I and into the respective bore I5 is a cylindrical tuning pin 52 coaxial with and of somewhat smaller diameter than the bore I5 and aperture 5I, the several pins 52 being supported byl a carrier 53. The carrier 53 is joined to one end of a metallic bellows 54, the other end of which is sealed hermetically to a cylindrical metalli'cm'ember 55 hermetically sealed in turn to the pole-piece body portion 41, as by means of a ring of solder indicated at 56.

The carrier 53 is mounted for controlled dis'- placement parallel to the length of the pins 52 to vary the proportion of the pinsinserted in the bores I5 and thereby to adjust the resonant frequency of the cavity resonators defined by these bores. Specically, an internally threaded cylindrical driving member 51 has its inner end aiiixed, as by soldering, to the bellows 54 and is slidably iitted within a cylindrical bearing or guide 58 which is secured to thev pole-piece 41 and locates the member 51 and the vcarrier 53 coaxially with the anode I3.

The driving member 51 has threaded thereinto a screw 59, the integral head 60 of which is supported for rotation upon a mounting plate 6I by means of ball bearings B2 disposed in a race deiined by an annular groove in the peripheral wall of the head 5B and the chainfered faces of a pair of bearing rings 54 and '55. The bearing ring E4 is secured to the mounting .plate 6I by screws, not shown; the bearing Iring B5 is mounted resiliently by an annular spring 86 'affixed to the mounting plate by a clamping 'ring accordingly. A Geneva stop 13, mounted upon the plate 6I cooperates with a pin 14 carried by the gear 10 to set the limits of rotation of the gear I0 in two directions and, thus, iixes the range of frequencies over which the cavity resonators may be tuned.

It will be appreciated that extremely fine tuning ofthe cavity resonators may be realized and that all of the resonators are tuned simult/aneously so that electrical symmetryVV of -the anode-cathode system is preserved. Because of the mounting of the `carrier 53 and, hence, of the tuning 'pins 52, in 'the manner. described; exact parallel motion -of the 'pins'axially of the bores I5 is attained so that'but va very smallclearance between'the pins'land the bore walls, is required; y

A 'suitable magnetic field in the cathode-anode region and having'its lines parallel to theA axis of the `cathode may be produced by a :pair of magnets 15 'havingtheir polesvabutting thepolepieces I1 ainduil. Inasmuch asithe pole-pieces extend into immediate proximity to the ends of the cathode and anode, fringingeiects areminimized and, lfurther, a 'highlyvefcient' magnetic system is attained'.

The ux in the anodeeoathode region maybe adjusted conveniently by one 'orzmore magnetic shunt pieces .'IS adapted to be inserted into slots in the fins l2 on the body III. l

Although a speciii'c embodiment of the inven tion has been shown and described, it willbe understood that it is;V butillustrative Aand that various modifications may be made therein without departing from rthe scope `and spirit :of this inventionias defined in the appended claims.

What is claimed is: i

l. An 'electron discharge `device comprising a first structure assembly including a body having a bore extending therethrough 'and a cylindrical anode within said lbore and coaxial therewith, said anode having portions deiining a plurality of tubular cavity resonators extending vparallel to the axis of-said anode, a cathode in coopera tive relation with said anode, a second structure assemblyiincluding arhollow member joined to said body and having thereon a guide extending parallel to said bore; said second assembly including also a driving' member located by said guide. for movement', in the direction parallel to said axis, 'a carrier xedly coupled 4to said driving member and a plurality of tuning members, 'one for each oflsai'd resonators and extending thereinto, mounted by said carrier, and means coupled thereto for moving said driving member-in said direction. f l

2. An electron discharge device comprising a hollow body dening a portion of an enclosing vessel,- ananode .rand af'cathode within said vessel, Asai-d anode. 'having portionsdeiining'a cavity resonator, a mounting member -joined to said body, a guide supported by said mounting member, a driving member slidably fitted within said guide for motion toward and away from said anode, a carrier mounted by said driving member, a tuning member supported by said carrier and extending into said cavity resonator, means including a flexible bellows forming a hermetic seal between said carrier and said mountingmember, and means coupled to said driving member for actuating it to displace said carrier and said tuning member, thereby to tune said cavity resonator.

3. An electron discharge device inl accordance with claim 2 wherein said actuating means comprises a screw, threaded into said driving member and supported rotatably by said mounting member, a helical gear coupled to said screw and supported thereby and a worm gear for driving said helical gear supported by said mounting member.

4. An electron discharge device comprising a hollow body defining a portion of an enclosing vessel, an anode within said body and having portions defining a plurality of parallel tubular cavity resonators therein, a cathode in cooperative relation with said anode, a plurality of tuning pins one for each of said resonators and extending therelnto, said pins being parallel to one another and to said resonators, a carrier member mounting said pins, a hollow mounting member joined to said body, means including a bellows Within said mounting member hermetically joining said carrier to said mounting member, a cylindrical guide within said mounting member and supported therefrom, said guide havingits axis parallel to said pins, a cylindrical driving member tted slidably within said guide and coupled to said carrier, and means coupled thereto for adjustably displacing said driving member parallel to its axis thereby to adjust the position of said pins within the resonators to tune said resonators.

5. An electron discharge device comprising a rst structure assembly including a body having a cylindrical bore extending therethrough and a cylindrical anode fitted in said bore and coaxial therewith, a second structure assembly including a cylindrical pole-piece ttcd within said bore and a cathode mounted by and coaxial with said pole-piece and encompassed by said anode, said anode having portions defining a plurality of tubular cavity resonators extending parallel to the axis of said anode and symmetrically about said axis, and a third structure assembly including a hollow second pole-piece joined to said body and in alignment with said first pole-piece, a cylindrical guide within said pole piece and mounted thereby in coaxial relation with said anode, a plurality oil tuning pins, one for each of said resonators and extending coaxially thereinto, means supporting said pins including acarrier to which said pins are afxed and a cylindrical driving member fitted slidably within said guide and coupled to said carrier, a bellows forming a hermetic seal between said second polepiece and said pin supporting means, and gear means mounted by said second pole-piece for axially displacing said driving member to efect tuning of said cavity resonators.

HERBERT C. JONAS. JOSEPH P. LAICO. VICTOR L. RONCI.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,106,768 Southworth Feb. 1, 1938 2,106,769 Southworth Feb. 1, 1938 2,396,802 Mouromtseff et al. Mar. 19, 1946 2,408,234 Spencer Sept. 24, 1946 2,422,465 Bondley June 17, 1947 

